1. Field of the Invention
The present invention relates to a data retrieving apparatus used in a multimedia system for efficiently retrieving data (below, multimedia data) which include character text data, animated picture data, sound data, still picture data, etc., by using a character-string which is provided by a user.
2. Description of the Related Art
Recently, storage media having large memory capacity, (for example, a CD-ROM, an optical-magnetic disk, etc.) have been widely utilized in various fields, and particularly, in multimedia systems. Accordingly, by utilizing such a storage medium having large memory capacity, it is relatively easy to structure a multimedia database which stores not only character text data, but also the animated picture data for an animation, the sound data for a voice and music, the still picture data for an illustration, etc.
On the other hand, many kinds of retrieval methods are provided for retrieving the character text data. Further, for the multimedia data, the user always requires a simplified and quick method for retrieving the multimedia data. Accordingly, the present invention aims to provide a simplified and quick method for retrieving the multimedia data.
In a conventional art, there are two representative methods for retrieving the character text data. One is a direct retrieving method in which text matching user supplied character string input is retrieved from the entire text of data; the other is a retrieving method for retrieving keywords which match the particular character-string provided by the user, and retrieving the text data using the keywords.
In the latter method, an index is previously provided by extracting important words from the text data as the keywords, and retrieving the keyword, which match the character-string provided by the user, from the index. The former is called "an all-context retrieving method", and the latter is called "a keyword retrieving method".
Further, in general, the all context retrieving method has an advantage which the user can freely select the character-string to be retrieved. However, since it is necessary to retrieve the character string, which matches the character-string provided by the user, by comparing the character-string with the text data for every character, a lot of time is required for retrieving only one character string when this method is executed.
On the other hand, the keyword retrieving method has an advantage which the user can quickly retrieve the character-strings compared to the all text retrieving method, but has a disadvantage which the user cannot freely input the character-string to be retrieved since kinds of words to be retrieved are restricted.